Lithium ion battery and battery pack

ABSTRACT

The present invention discloses a lithium ion battery, including a battery shell, a battery top cap mounted on the battery shell, and a relief valve provided on the battery shell and/or the battery top cap; the lithium ion battery further includes a safety protection device that is provided on the battery shell and/or the battery top cap and that fixedly fits with the relief valve; where the safety protection device includes a baffle plate opposite to the relief valve, a side wall and a gas flow channel structure; the side wall extends, from the baffle plate, toward the battery shell or the battery top cap, and is connected with the battery shell or the battery top cap; and the gas flow channel structure is formed on the side wall. By forming the gas flow channel structure on the side wall, the baffle plate and the gas flow channel structure form a relatively separate design, so that the baffle plate may be used for effectively baffling solid spark particles, and meanwhile the lateral gas flow channel structure may be used for effectively discharging gases, thereby improving the safety performance of the lithium ion battery.

TECHNICAL FIELD

The present invention relates to the field of a lithium ion battery, and more particularly, to a lithium ion battery and a battery pack.

BACKGROUND

With an increasingly wide application of a lithium ion battery to an electric automobile and power grid energy storage or other fields, the safety performance of the lithium ion battery has drawn more and more attentions. A cause for a safety problem of the lithium ion battery generally is thermal runaway.

When thermal runaway occurs in the lithium ion battery, the heat release of an active material inside the lithium ion battery may reach hundreds of joules per gram. Instantaneous heat production may trigger a sharp redox reaction between the active material and electrolyte, and produce a great deal of combustible gas, which may sharply raise internal pressure of the battery, thereby bursting an anti-explosion valve to form a rapid gas flow, the jetted combustible gas may touch and mix with air; simultaneously, in the process of emission of the combustible gas inside the battery, a great number of high-temperature solid particles may be jetted out. These solid particles may form bright sparks and ignite the mixture of air and the combustible gas, thereby causing a combustion or even an explosion.

A Chinese Patent Application Publication No. CN103474599A discloses a lithium ion battery having a through-hole mesh enclosure with an ideal safety and a battery pack. High-temperature solid particles may be filtered out by means of the mesh enclosure, thereby achieving an objective of separating the combustible gas from the high-temperature solid particles. However, the inventor of the present application found that the mesh enclosure according to the Chinese Patent Application Publication No. CN103474599A still has some defects: when thermal runaway occurs on the battery, the combustible gas inside the battery may be rapidly jetted together with the high-temperature solid particles. Because through holes on the mesh enclosure are merely provided on a top surface of the mesh enclosure and positioned in a direction of gas emission, if the through holes on the top surface of the mesh enclosure are too large, under the action of a high-speed gas flow, the high-temperature solid particles may be jetted from inside the battery to cause a combustion or even an explosion. Furthermore, too large through holes may reduce the intensity of the mesh enclosure, and the mesh enclosure may easily be damaged under the impact of the high-speed gas flow mixed with the high-temperature solid particles. However, if the through holes are too small, the gas flow may not be timely discharged from inside the battery, thereby reducing gas emission efficiency. Additionally, in case of thermal runaway inside the battery, a molten plastic component, solid particles or metal slag jetted with the gas flow may block a mesh hole, resulting in a sharp rise of the internal pressure of the battery, which may have a higher risk of causing an explosion.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to provide a lithium ion battery having good safety performance and a battery pack.

The present invention is implemented in such a way: a lithium ion battery is provided, including a battery shell, a battery top cap mounted on the battery shell, and a relief valve provided on the battery shell and/or the battery top cap; the lithium ion battery further includes a safety protection device that is provided on the battery shell and/or the battery top cap and that fixedly fits with the relief valve; where the safety protection device includes a baffle plate opposite to the relief valve, a side wall and a gas flow channel structure; the side wall extends, from the baffle plate, toward the battery shell or the battery top cap, and is connected with the battery shell or the battery top cap; and the gas flow channel structure is formed on the side wall.

Further, the gas flow channel structure is only provided on the side wall.

Further, the gas flow channel structure formed on the side wall includes at least one opening structure, at least one through-hole array or at least one gap.

Further, when the gas flow channel structure is a through-hole array, an area of each through hole in the through-hole array is not less than 1 mm².

Further, the baffle plate is provided with a plurality of through holes, and an area of each through hole on the baffle plate is less than 1 mm².

Further, the gas flow channel structure includes a first gas flow channel and a second gas flow channel separately formed on the side wall; the first gas flow channel is one of the opening structure, the through-hole array and the gap; the second gas flow channel is one of the opening structure, the through-hole array and the gap; and the first gas flow channel is different from the second gas flow channel in structure.

Further, the relief valve includes a relief hole; and a sum of an area of the gas flow channel structure is not less than 0.5 times of that of the relief hole.

Further, when the first gas flow channel or the second gas flow channel is a through-hole array, an area of each through hole in the through-hole array is not less than 1 mm².

Further, the lithium ion battery further includes a cell housed in the battery shell; the safety protection device is provided between the cell and the battery top cap; a height of the safety protection device is at least 1 mm less than a minimum distance from the cell to a surface of the battery top cap and adjacent to the cell; a spacing between a side of the safety protection device and an internal surface of the battery shell is not less than 1 mm; and a length of the safety protection device is at least 1 mm less than a minimum spacing between a positive tab and a negative tab of the cell.

Further, the safety protection device further includes a connection part; the connection part is provided at an end of the side wall and is provided separately from the baffle plate; and the side wall is connected, by means of the connection part, with the battery shell or the battery top cap.

Further, the lithium ion battery further includes another safety protection device; the another safety protection device and the safety protection device are provided at two sides of the relief valve, and respectively cover the relief valve; the another safety protection device includes a baffle plate opposite to the relief valve, a side wall and a gas flow channel structure; the side wall extends, from the baffle plate, toward the battery shell or the battery top cap, and is connected with the battery shell or the battery top cap; and the gas flow channel structure is formed on the side wall and/or the baffle plate.

Further, the safety protection device is made from a metallic material or an inorganic non-metal ceramic material.

Further, a surface of the safety protection device is provided with a teflon coating, an epoxy resin coating, a phenolic resin coating, a polyethylene terephthalate coating, a polypropylene coating or a ceramic coating.

The present invention further provides a lithium ion battery pack, including a plurality of the foregoing lithium ion batteries connected in parallel and/or in series.

In the lithium ion battery pack and the lithium ion battery according to an embodiment of the present invention, by forming the gas flow channel structure of the safety protection device on the side wall, the baffle plate of the safety protection device and the gas flow channel structure form a relatively separate design, so that the baffle plate may be used for effectively baffling solid spark particles, and the gas flow channel structure positioned on a side of the safety protection device may be used for effectively jetting gas, thereby reducing a risk of explosion resulted from internal pressure increased due to insufficiency in the gas emission efficiency, and improving the safety performance of the lithium ion battery. Also, a gas flow direction may be diverted by using the baffle plate and the gas flow channel structure positioned on a side of the safety protection device, thereby avoiding smoke and gas vertically jetted at a high speed from mixing with air on a large scale, and further improving the safety performance of the lithium ion battery.

DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic exploded pictorial drawing of the lithium ion battery according to an embodiment of the present invention.

FIG. 2 is a schematic enlarged drawing of the safety protection device of the lithium ion battery in FIG. 1.

FIG. 3 is a top view of the safety protection device in FIG. 2.

FIG. 4 is a front view of the safety protection device in FIG. 2.

FIGS. 5-11 are schematic diagrams of several specific implementation manners of the safety protection device according to the embodiments of the present invention.

FIG. 12 is a schematic exploded pictorial drawing of the lithium ion battery according to another embodiment of the present invention.

SPECIFIC EMBODIMENTS

Detailed description of the present invention will further be made with reference to the accompanying drawings and the embodiments in order to make technical problems, technical solutions and beneficial effects of the present invention clearer. It is to be understood that the embodiments described herein are only used to explain the present invention, but are not intended to limit the present invention.

FIG. 1 is a schematic exploded pictorial drawing of the lithium ion battery according to an embodiment of the present invention. As shown in FIG. 1, the lithium ion battery includes a battery shell 10, a cell 20 provided in the battery shell 10, electrolyte (not shown) perfused into the battery shell 10, and a battery top cap 50 mounted on the battery shell 10. The battery top cap 50 is provided with a positive terminal and a negative terminal 505 (the positive terminal and the negative terminal are not distinguished in the figure), the positive terminal and the negative terminal 505 each are electrically connected, by means of an electrical connection body 30, with an anode and a cathode of the cell 20. A relief hole 510 is provided at a central position between the positive terminal and the negative terminal 505 of the battery top cap 50, and the relief hole 510 is hermetically provided with an anti-explosion relief disk 60. The relief disk 60 and the relief hole 510 jointly constitute a relief valve.

Specifically, the relief disk 60 may be made from the same metallic material as that of the battery top cap 50, so that a problem of formation of an electrolytic cell by ambient air or electrolyte and different metals due to existence of electric potential difference thereamong may be overcome, and a risk of corrosion reaction may be reduced. In an implementation manner as shown in FIG. 1, the relief disk 60 may be made from one of aluminum, aluminum alloy, nickel, nickel alloy and stainless steel. The relief disk 60 has good malleability, and does not fly off during pressure relief by rupture. According to an implementation manner of the present invention, the relief disk 60 may be coated or bonded with a layer of corrosion-resistant material, for example, PE and/or PP, which may prevent the relief disk 60 from being corroded by the electrolyte. According to another implementation manner of the present invention, the relief disk 60 is provided with a weakness line or a weakness surface, the weakness line or the weakness surface ruptures first in case that the internal pressure of the battery is too high, so that the rupture position of the relief disk 60 is controllable. According to an implementation manner of the present invention, the relief disk 60 can bear a pressure of 0.3-1.2 MPa when it reaches a critical state of rupture.

As shown in FIG. 1, the lithium ion battery further includes a safety protection device 40 fixedly fitting in with the relief valve. The safety protection device 40 may be provided on a first surface that is on the battery top cap 50 and is opposite to the cell 20, for example, a lower surface (when the lithium ion battery is mounted at a position as shown in FIG. 1), and is positioned between the battery top cap 50 and the cell 20. According to an implementation manner of the present invention, in a direction from the battery top cap 50 to the cell 20, the safety protection device 40 may be provided right under the relief disk 60.

Specifically, as shown in FIGS. 2-4, the safety protection device 40 includes a baffle plate 48 opposite to the relief valve, a side wall 49, a connection part 42 and a gas flow channel structure 41.

In an embodiment, the baffle plate 48 may cover right under the relief disk 60, and a projected area of the baffle plate 48 on the relief valve is not less than 1.0 times of an area of the relief valve, so that sparks jetted in front may be better baffled, and the sparks may generate a reflection so as to change a motion curve and an emission velocity. In an embodiment as shown in FIG. 2, the baffle plate 48 is a continuous structure, namely, the baffle plate 48 is not provided with a through hole for the gas flow passing through, or in other words, the gas flow channel structure is only provided on the side wall, so that sparks jetted in front may be completely baffled, and the sparks may generate a reflection so as to change a motion curve and an emission velocity.

The side wall 49 is provided on the baffle plate 48 roughly perpendicularly or obliquely, and extends, from the baffle plate 48, toward the battery top cap 50. The side wall 49 may be continuously provided along a fringe of the baffle plate 48 (as shown in FIGS. 6, 7, 9 and 10), or be discontinuously provided along the fringe of the baffle plate 48 (as shown in FIGS. 2, 5 and 8). In an embodiment as shown in FIG. 2, the side wall 49 is discontinuously provided along the fringe of the baffle plate 48; and the side wall 49 includes two side plates provided on the baffle plate 48 roughly perpendicularly or obliquely.

The connection part 42 is provided at an end of the side wall 49 and is provided separately from the baffle plate 48. The connection part 42 is fixed to the battery top cap 50. The connection part 42 may be integrated with the battery top cap 50 into one piece by means of stamping or molding and the like, or be connected and fixed to the battery top cap 50 by means of bonding, welding, riveting, clamp connection, threaded connection, buckle connection or the like. In an embodiment, the connection part 42 may be fixed to the battery top cap 50 by means of welding, so that a connection force is not less than 50N. If the connection force is too small, vibration in the process of manufacturing and assembly of the battery or in the process of subsequent use of the battery may easily cause the safety protection device 40 to fall off. In the process of actual use, as shown in FIG. 11, the connection part 42 may be left out according to an actual situation, and the side wall 49 may be directly connected and fixed to the battery top cap 50 by means of bonding, welding, buckle connection or the like.

The gas flow channel structure 41 is formed on the side wall 49. In an embodiment as shown in FIG. 2, the gas flow channel structure 41 includes a first gas flow channel 46 formed on a side plate of the side wall 49, and a second gas flow channel 44 formed between two side plates of the side wall 49. The first gas flow channel 46 includes an opening structure formed on a side plate; the opening structure may be a completely-opened rectangular hole as shown in FIG. 2 or a hole of other shapes, so that the side plate is roughly shaped like a frame. A sum of an area of the opening structure is not less than 0.5 times of that of the relief hole 510. If the area is too small, gas inside the battery is unable to be discharged timely when inside of the battery loses efficacy, which may cause gathering of gas pressure inside the battery to go beyond a burst pressure limit of the shell, and cause the shell to burst or even to explode. The second gas flow channel 44 may be a gap between two side plates of the side wall 49, and it may be construed as below: the side wall 49 may be continuously provided along a fringe of the baffle plate 48, the second gas flow channel 44 is a notch formed on the side wall 49, i.e., a part that is positioned between the two side plates and positioned between a free end of the side wall 49 and the baffle plate 48 is cut off completely.

In practical application, the safety protection device 40 may be made from a metallic material or an inorganic non-metal ceramic material. In an embodiment, the safety protection device 40 may be made from a metallic material such as aluminum, aluminum alloy, nickel, nickel alloy or stainless steel. And the safety protection device 40 may be made from the same metallic material as that of the battery top cap 50. This is because the safety protection device and the battery shell of different materials may form an electrochemical cell in an electrolyte in moist environment, which may reduce reliability of the battery. At least a surface of the safety protection device 40 toward the cell 20 (for example, a surface at one side of the safety protection device 40 far away from the relief valve when the safety protection device 40 is positioned between the battery top cap 50 and the cell 20; a surface at one side of the safety protection device 40 facing the relief valve when the safety protection device 40 is positioned outside the battery top cap 50) may be sprayed with a teflon coating, an epoxy resin coating, a phenolic resin coating, a polyethylene terephthalate (PET) coating, a polypropylene (PP) coating, a ceramic coating or the like for performing an insulating treatment. The coating, having a thickness not less than 10 um, needs to be uniformly coated on a metal surface. Drain metal may easily occur when the coating thickness is too thin. The coating may effectively achieve effects of insulation and anticorrosion. A risk of short circuit due to connection of a positive electrode and a negative electrode may exist if surface insulation of the safety protection device 40 is not good enough.

In practical application, as shown in FIG. 4, a height H from the connection part 42 of the safety protection device 40 to the baffle plate 48 is at least 1 mm less than a spacing from a first surface (for example, a lower surface) of the battery top cap 50 to an upper surface of the cell 20. If the height H is too large, the baffle plate 48 may squeeze a positive electrode plate and a negative electrode plate of the cell 20, which may cause the electrode plates to deform or even cause a short circuit between the positive electrode and the negative electrode. A length L between two side walls 49 of the safety protection device 40 is at least 1 mm less than a minimum spacing between a positive tab and a negative tab. If the length L is too large, the tabs may easily form interference with a border edge between the baffle plate 48 and the side wall 49, which may easily damage the tabs. As shown in FIG. 1 and FIG. 2, a width W of the safety protection device 40 is at least 1 mm less than a spacing of an internal surface S of the shell 10. If the width W is too large in distance, assembly of the battery top cap 50 and the shell 10 may be interfered with.

When a safety test is performed on the lithium ion battery after assembly according to the implementation manner as shown in FIG. 1, the internal temperature of the lithium ion battery sharply rises and a great deal of smoke and gas is produced. At the moment, the relief disk 60 ruptures and overturns to release the smoke and gas, mingled with high-temperature solid spark particles, inside the lithium ion battery. Because the safety protection device 40 for covering the relief disk 60 is provided under the relief disk 60, the solid spark particles sputtered out are baffled by the baffle plate 48 of the safety protection device 40. Meanwhile, the smoke and gas may be successfully discharged from the battery shell 10 through the first gas flow channel 46 and the second gas flow channel 44, and the function of pressure relief may be still maintained.

In this process, the motion curve of the solid spark particles sputtered out mainly is a straight line. Therefore, when the solid spark particles sputtered out flow with the smoke and gas into the safety protection device 40, the solid spark particles sputtered out may be bounced, by the baffle plate 48 of the safety protection device 40, back to inside the shell 10, thereby preventing the high-temperature solid spark particles along with a high-speed gas flow from jetting outside the battery, and reducing a risk of the smoke and gas burning outside the battery. Simultaneously, when the smoke and gas jetted at a high speed flow to the safety protection device 40, the smoke and gas are baffled by the baffle plate 48 of the safety protection device so that a flow direction thereof is diverted, and the smoke and gas are discharged from the first gas flow channel 46 and the second gas flow channel 44 which are positioned on a side of the safety protection device 40, thereby reducing an emission speed of the smoke and gas jetting outside the battery, reducing an emission distance of the smoke and gas, and reducing a contact area between the smoke and gas and air. In this way, a risk of burning of combustible gas may be reduced. In addition, it is possible to reduce a possibility of burning resulted from contact of the smoke and gas with other external substances by reducing the jet speed of the smoke and gas jetting out of the battery, thereby avoiding causing greater losses.

As mentioned above, compared with the Chinese Patent Application Publication No. CN103474599A, in the safety protection device 40 according to an embodiment of the present invention, by means of a relatively separate design of the baffle plate 48 and the first gas flow channel 46 and the second gas flow channel 44, the baffle plate 48 may be used for effectively baffling solid spark particles, and the first gas flow channel 46 and the second gas flow channel 44 which are positioned on a side of the safety protection device 40 may be used for efficiently discharging gas. In this way, a risk of explosion resulted from increase of internal pressure due to insufficiency in gas discharge efficiency may be reduced. Also, a gas flow direction may be diverted by using the baffle plate 48, and the first gas flow channel 46 and the second gas flow channel 44 which are positioned on a side of the safety protection device 40, thereby avoiding mixing the smoke and gas vertically jetted at a high speed with air on a large scale. Therefore, the safety protection device 40 according to an embodiment of the present invention may separate the smoke and gas jetted at a high speed, for example, combustible gas or electrolyte steam, from the solid spark particles, to prevent the combustible gas or the electrolyte steam from jetting along with the solid spark particles and from burning by mixing with air at an area far away from the relief valve. Filtration of the solid spark particles may effectively change a possible ignition mode of the battery from spark ignition to spontaneous ignition of the smoke and gas. From a physical standpoint, a temperature for igniting the smoke and gas generally is lower than 60 degrees, but a spontaneous ignition temperature of the smoke and gas generally is higher than 450 degrees. In this way, the safety protection device 40 may significantly improve the safety performance of the lithium ion battery.

Additionally, compared with the Chinese Patent Application Publication No. CN103474599A, the present invention has a relatively separate design of the baffle plate 48 and the first gas flow channel 46 and the second gas flow channel 44, and the baffle plate 48 is positioned in a direction from which gas is jetted. Therefore, the baffle plate 48 may effectively baffle the solid spark particles, and the first gas flow channel 46 and the second gas flow channel 44 which are positioned on a side of the safety protection device 40 may be not subjected to a direct impact from the solid spark particles or may merely be subjected to a direct impact from a small number of the solid spark particles. Therefore, sizes and shapes of the first gas flow channel 46 and the second gas flow channel 44 may have a wider range of choice, thereby ensuring a high-efficiency gas discharge and not easily being blocked by the solid spark particles, etc.

FIG. 5 illustrates a three-dimensional schematic diagram of the safety protection device according to an implementation manner of the present invention. The safety protection device in FIG. 5 is similar to that in FIG. 2, and a main difference between the two lies in that: the first gas flow channel 46 of the safety protection device in FIG. 5 includes multiple through holes formed on the side wall, i.e., a through-hole array. In an embodiment, the area of each through hole is not less than 1 mm², and the total area of through holes is not less than 0.5 times of the area of the relief hole 510. The safety protection device in FIG. 5 may comprehensively balance a sparks baffle effect and a gas discharge velocity.

FIG. 6 illustrates a three-dimensional schematic diagram of the safety protection device according to an implementation manner of the present invention. The safety protection device in FIG. 6 is similar to that in FIG. 5, and a main difference between the two lies in that: the side wall 49 is continuously provided along a fringe of the baffle plate 48, and the second gas flow channel 44 includes multiple through holes formed on the side wall, i.e., the first gas flow channel 46 and the second gas flow channel 44 each include multiple through holes formed on the side wall, i.e., a mesh structure with mesh holes. A shape of the through hole may be a round, a rhombus, a square, an ellipse, a racetrack or the like. The area of each through hole is not less than 1 mm², and the total area of the through holes is not less than 0.5 times of the area of the relief hole 510. If the area of a single through hole is too small, on one hand, it is difficult to ensure a requirement of the gas flow channel for an area, on the other hand, both a molten plastic component and solid particles inside the battery may easily block mesh holes, thereby leading to failure of timely emission of gas, and leading to gathering of internal pressure and thus causing a potential safety hazard. The first gas flow channel 46 and the second gas flow channel 44 adopt a mesh structure with mesh holes, which may effectively baffle sparks possibly escaping from the first gas flow channel 46 and the second gas flow channel 44, and better separate sparks from the combustible gas.

FIG. 7 illustrates a three-dimensional schematic diagram of the safety protection device according to an implementation manner of the present invention. The safety protection device in FIG. 7 is similar to that in FIG. 2, and a main difference between both lies in that: the side wall 49 of the safety protection device in FIG. 7 is continuously provided along a fringe of the baffle plate 48, and the second gas flow channel 44 includes a plurality of through holes formed on the side wall. In an embodiment, the area of each through hole is not less than 1 mm², and the total area of the through holes is not less than 0.5 times of the area of the relief hole 510. The safety protection device in FIG. 7 may comprehensively balance a sparks baffle effect and a gas discharge velocity.

FIG. 8 illustrates a three-dimensional schematic diagram of the safety protection device according to an implementation manner of the present invention. The safety protection device in FIG. 8 is similar to that in FIG. 2, and a main difference between the two lies in that: the baffle plate 48 is provided with multiple through holes, i.e., the baffle plate 48 is a mesh structure with mesh holes. The through holes on the baffle plate 48 may only allow gas to pass through, but not allow the high-temperate solid particles to pass through. For example, in an embodiment, a single through hole having an area smaller than 1 mm² may effectively increase the area of a gas flow channel, and reduce a gathering degree of internal gas pressure of the shell 10. If the area of a single hole is too large, a part of sparks with smaller particle sizes may possibly pass through the hole, and thus the sparks baffle effect may be deteriorated.

FIG. 9 illustrates a three-dimensional schematic diagram of the safety protection device according to an implementation manner of the present invention. The safety protection device in FIG. 9 is similar to that in FIG. 7, and a main difference between the two lies in that: the baffle plate 48 is provided with multiple through holes, i.e., the baffle plate 48 is a mesh structure with mesh holes. The through holes on the baffle plate 48 may only allow gas to pass through, but not allow the high-temperate solid particles to pass through. For example, in an embodiment, a single through hole having an area smaller than 1 mm² may effectively increase the area of the gas flow channel. The safety protection device in FIG. 9 may effectively balance a sparks baffle effect and a gas discharge velocity.

FIG. 10 illustrates a three-dimensional schematic diagram of the safety protection device according to an implementation manner of the present invention. The safety protection device in FIG. 10 is similar to that in FIG. 2, and a main difference between the two resides in that: the side wall 49 of the safety protection device in FIG. 10 is continuously provided along a fringe of the baffle plate 48, and the second gas flow channel 44 includes an opening structure formed on the side wall, so that the side plate is roughly shaped like a frame. The safety protection device in FIG. 10 may enhance an intensity of the safety protection device.

FIG. 12 is a schematic exploded pictorial drawing of the lithium ion battery according to another implementation manner of the present invention. The lithium ion battery in FIG. 12 is similar to that in FIG. 1, and a main difference between the two lies in that: the lithium ion battery in FIG. 12 further includes another safety protection device 70, both the safety protection device 70 and the safety protection device 40 are provided at two sides of the battery top cap 50, and respectively cover the relief disk 60. A structure of the safety protection device 70 may be the same as that of any safety protection device 40 in the foregoing embodiments. In addition, the safety protection device 70 may dispose the gas flow channel structure only on the baffle plate 48. Both the safety protection device 40 and the safety protection device 70 provide double protection for the safety of the cell 20 in the process of a safety test of the cell. While the gas flow channel is ensured to be unblocked, an effective double baffle of the solid spark particles may be imposed, which may separate the solid spark particles from the smoke and gas such as combustible smoke and gas more effectively, thereby ensuring the safety of the cell 20.

It should be noted that, in a graphical implementation manner, the lithium ion battery is a square lithium ion battery. However, it is to be understood that, the present invention has no special restriction on the shape of the lithium ion battery. The lithium ion battery may be a lithium ion battery of other shapes, for example, a prismatic lithium ion battery or a cylindrical lithium ion battery. Additionally, in the embodiments shown in the figures, although the present invention is described only by taking the relief disk as an example, the safety protection device as depicted in the present invention may also be applied to relief valves of other lithium ion batteries. In addition, the safety protection device may also be provided on the shell 10 in any manner as similar to above, or be respectively provided on the shell 10 and the battery top cap 50.

The above descriptions are only preferred embodiments of the present invention, which are not used to limit the present invention. Any modification, identical substitution and improvement made within the spirit and principle of the present invention shall be included in the scope of protection of the present invention. 

1. A lithium ion battery, comprising a battery shell, a battery top cap mounted on the battery shell, and a relief valve provided on the battery shell and/or the battery top cap; wherein the lithium ion battery further comprises a safety protection device that is provided on the battery shell and/or the battery top cap and that fixedly fits with the relief valve; the safety protection device comprises a baffle plate opposite to the relief valve, a side wall and a gas flow channel structure; the side wall extends, from the baffle plate, toward the battery shell or the battery top cap, and is connected with the battery shell or the battery top cap; and the gas flow channel structure is formed on the side wall.
 2. The lithium ion battery according to claim 1, wherein the gas flow channel structure is only provided on the side wall.
 3. The lithium ion battery according to claim 1, wherein the gas flow channel structure formed on the side wall comprises at least one opening structure, at least one through-hole array or at least one gap.
 4. The lithium ion battery according to claim 3, wherein when the gas flow channel structure is a through-hole array, an area of each through hole in the through-hole array is not less than 1 mm².
 5. The lithium ion battery according to claim 1, wherein the baffle plate is provided with a plurality of through holes, and an area of each through hole on the baffle plate is less than 1 mm².
 6. The lithium ion battery according to claim 1, wherein the gas flow channel structure comprises a first gas flow channel and a second gas flow channel separately formed on the side wall; the first gas flow channel is one of the opening structure, the through-hole array and the gap; the second gas flow channel is one of the opening structure, the through-hole array and the gap; and the first gas flow channel is different from the second gas flow channel in structure.
 7. The lithium ion battery according to claim 3, wherein the relief valve comprises a relief hole; and a sum of an area of the gas flow channel structure is not less than 0.5 times of that of the relief hole.
 8. The lithium ion battery according to claim 6, wherein when the first gas flow channel or the second gas flow channel is a through-hole array, an area of each through hole in the through-hole array is not less than 1 mm².
 9. The lithium ion battery according to claim 1, wherein the lithium ion battery further comprises a cell housed in the battery shell; the safety protection device is provided between the cell and the battery top cap; a height of the safety protection device is at least 1 mm less than a minimum distance from the cell to a surface of the battery top cap that is adjacent to the cell; a spacing between a side of the safety protection device and an internal surface of the battery shell is not less than 1 mm; and a length of the safety protection device is at least 1 mm less than a minimum spacing between a positive tab and a negative tab of the cell.
 10. The lithium ion battery according to claim 1, wherein the safety protection device further comprises a connection part; the connection part is provided at an end of the side wall and is provided separately from the baffle plate; and the side wall is connected, by means of the connection part, with the battery shell or the battery top cap.
 11. The lithium ion battery according to claim 1, wherein the lithium ion battery further comprises another safety protection device; the another safety protection device and the safety protection device are provided at two sides of the relief valve, and respectively cover the relief valve; the another safety protection device comprises a baffle plate opposite to the relief valve, a side wall and a gas flow channel structure; the side wall extends, from the baffle plate, toward the battery shell or the battery top cap, and is connected with the battery shell or the battery top cap; and the gas flow channel structure is formed on the side wall and/or the baffle plate.
 12. The lithium ion battery according to claim 1, wherein the safety protection device is made of a metallic material or an inorganic non-metal ceramic material.
 13. The lithium ion battery according to claim 12, wherein a surface of the safety protection device is provided with a teflon coating, an epoxy resin coating, a phenolic resin coating, a polyethylene terephthalate coating, a polypropylene coating or a ceramic coating.
 14. A lithium ion battery pack, comprising a plurality of lithium ion batteries connected in parallel and/or in series according to any one of claim
 1. 15. The lithium ion battery according to claim 6, wherein the relief valve comprises a relief hole; and a sum of an area of the gas flow channel structure is not less than 0.5 times of that of the relief hole 